Horses and Diphtheria

Written by Phillip Nguyen and Gavin Martindale

About Diphtheria

Diphtheria is a bacterial disease that starts with the symptoms comparable to today’s common cold. The disease is caused by “Klebs-Loeffler bacilli” which is also referred to as “Diphtheria bacilli” or Corynebacterium diphteriae (Fulham 1933, 26).  Diphtheria is now known to be spread by direct contact or air. The infection causes thick patches “pseudo-membrane” to develop in the back of the throat which can lead to complications. Once in the respiratory system, the bacteria produces a toxin which can cover tissues in the nose, tonsils, voice box, making it hard to breathe and swallow. The toxin may also get into the blood stream and cause damage to the heart, kidneys, and nerves (CDC Diphtheria). The disease causes extreme discomfort and eventually ends up practically strangling one to death. The disease affects all ages, but seems to have its greatest effects on children from age 2-10 years old which is shown through a Medical Officer’s of Health for the London County Council report in 1910. This report showed that in 1910 in the “Four weeks preceding weeks of holiday influence” from the age 0-3 there were 72 cases noted, from 3-10 there were 268, and from 13 upwards there were 45 (London County Council 1910, 40). Though diphtheria is now a treatable disease by antibiotics, antitoxins, or by simple vaccination, it was once a major cause of illness and death. This was especially the case for children. Before there was treatment for diphtheria, up to half of the people who got the disease died from it (CDC Diphtheria).

Originally many doctors were unable to determine what caused people to contract diphtheria. For instance, in the 1897, the MOH of Stoke Newington reported that there were 53 cases where 7.5% were due to “insanitary conditions in homes” and another 7.5% for “school attendance,” while in “39 cases I was unable to trace the origin of the disease” (Stoke Newington 1897, 37). The MOH of Hackney 1897 report also claims that the majority of the cases “baffle our efforts to trace them to their source” (Hackney 1897, 14). However, later doctors realized that the disease was “mainly spread from person to person” by means of “respiratory channels” (Fulham 1933, 36). This transfer of the disease is through means of direct contract or via air through acts like coughing. It may seem bizarre, but doctors seemed to have found a working cure for the disease before they found the source of the disease.

Diphtheria antitoxin

In 1894, Dr. Behring found that the main way to prevent the effects and even cure diphtheria was through the “administration of serum” (Hendon 1938, 85). The cure is composed of the “blood serum of horses” into which the diphtheria bacilli had been injected (Fulham 1933, 29). Other animals were tested, but horses supplied the most serum, and were the “least infected by the injection of the toxin” (Warner 2013). This discovery revolutionized the treatment of the disease and decreased the mortality or death rate significantly. The diphtheria anti-toxic serum contains the blood serum of horses in which increasing doses of diphtheria toxin (a filtrate of a liquid culture of diphtheria bacilli) have been injected (Fulham 1933, 29). The small doses of this specific toxin of diphtheria in horses does not cause diphtheria in the horses, but instead increase the horse’s resistance to the disease. The horse will actively produce antitoxins which can then be separated from the blood.  The whole process is complicated as both the toxin and the antitoxin have to be standardized and precautions are taken regarding cleanliness, asepsis, and absence of disease in the horse (Fulham 1933, 29).

A horse which was being used to produce diptheria antitoxin.

Diphtheria antitoxin, produced in horses, was used for treatment of diphtheria in the UK and in the United States beginning in the 1890s (Epidemiology and Prevention of vaccine-Preventable Diseases). The serum was incredibly effective if used before disease had spread too much, but the anti-toxin only seemed to be used by the people who could afford it. This led public health officials in London to call for an order to provide a “temporary supply of diphtheria anti-toxin for poorer inhabitants” (London County Council 1910, 40). This made the serum more readily available which lead to greater “opportunity for early treatment” (London County Council 1910, 40).  A table shown in the London County Council 1934 report shows that the “total number of diphtheria antitoxin units supplied” in 1910 was 68,488,000, and in 1934 the number was 579,012,000 which shows how effective this serum was due to its increase in demand of supplies (London County Council 1934, 172).

Although the serum seemed to be extremely effective, as in the case of most bacterial diseases, the bacteria began to develop resistance. The disease seemed to “have streptococci in addition to diphtheria bacilli” which increased the fatality rate until a vaccine was created (East Ham 1928, 38). An example of this rise in fatality can be seen in a table of the Finsbury 1910 report where it shows the total amount of infant deaths in 1907 to be 2 while in 1910 it increased to 4 (Finsbury 1910, 38). This may seem like a small jump in number, but at that time the serum was still new and this slight jump might not have been recognized to be caused by the gaining strength of bacteria in the sixteen years since the serum had been actively used. Another aspect that came along with time due to the realization of the effectiveness of horse serum was the ability to check for immunity of diphtheria. Doctors began to realize that some people were immune to the disease which led to the Schick Test. This test was “made routine” mainly for infants. It decided if they could start immunizing earlier on, or if they should just be ready if symptoms seemed to arise (Holborn 1925, 55).

However, even after the introduction of diphteria antitoxin, mortality rates remained high because in many cases, treatment did not occur until too late. The longer anti-toxin treatment is delayed, the less the chance of the patient’s recovery; for every day’s delay the case mortality rises rapidly (Fulham 1933, 29). The MOH of Fulham noted that the early administration of the diphtheria antitoxin was the main reason for the decrease in mortality in his district. It is important to note that the antitoxin will not perform for toxins that have already bonded to tissue.

Diphtheria antitoxin produced by inoculating horses with concentrated doses of diphtheria bacteria.

According to the MOH of Hendon, it was helpful in some cases of diphtheria to give continuous intravenous drip saline with 5% dextrose by means of the apparatus known as the Vacoliter (Hendon 1938, 86). The technique was performed at the Hendon Isolation Hospital with promising results. However, administration of the horse serum remained the main method for treating diphtheria. According to the MOH for Kensington, it appears that treatment was most successful at hospitals where the antitoxin serum was administered in larger doses. On the other hand, the mortality was greatest at the hospitals at which the smallest and the fewest doses were given, and at which the fewest cases, in proportion to total cases, were thus treated (Kensington 1896, 52). Concentrated serums allowed for more units of antitoxin in smaller bulk of horse serum is a definite advantage. The made it possible to give massive dosage of antitoxin without the disturbing factor of serum sickness (Hendon 1938, 85).

The MOH for Hampton stated that most suspicious cases of sore throat were injected with the antitoxin serum and then swabbed. The swab was then sent to the Clinical Research Association for further analysis. If the result turned out to be negative, no harm resulted; if positive, great advantage accrued by having the antitoxin injected early (Hampton 1911, 18). In addition to a positive diphtheria case, the MOH of Hampton recommended that the rest of the household be injected with small doses of the antitoxin serum. We see here that the MOH of Hampton’s protocol correlated with that of the MOH of Fulham in that early administration is essential in neutralizing the disease. According to the MOH of Kingston, the injection of the anti-toxin has no effect on persons not suffering from diphtheria, so that there was no reason for delay (Kingston upon Thames 1897, 8). The Kingston MOH compiled a table of the mortality rates of cases treated on different days of the illness. Although the results with antitoxin were always more favorable, the results of its use on the first day of the disease still show the most marked difference (Kingston upon Thames 1897, 8). It has been so clearly shown that the earlier antitoxin is given in the disease the better is the chance of recovery that every advantage should be taken of this fact; a possible source of delay in administering antitoxin is if the doctor sees a patient and after examination he suspects that he is dealing with a case of diphtheria he merely takes a swab for bacteriological examination and does not inject antitoxin at once, but delays till he hears the result of the bacteriological examination some 24 hours or so later (Holborn 1925, 55). In short, the percentage of mortality is lower for those administered with the antitoxin serum on the first day of illness.

Mortality rates for diphtheria began to improve as the treatment with antitoxin became standardized. In statistics compiled by the MOH of Finsbury, he found that in 1894, 3,042 patients of all ages were treated in the Board’s Hospitals without antitoxin. 902 died, yielding a mortality of 29.6% (Finsbury 1902, 63). However in 1895, the antitoxin serum treatment was inaugurated; 3,529 cases of Diphtheria were treated, and 729 died, yielding a mortality of 22.5% (Finsbury 1902, 63). Not only were more people treated, but there was also a lower mortality rate. Hence, in the first year there was a fall in mortality of 7.1% (Finsbury 1902, 63).

Home treatment vs. hospital treatment also play a role in mortality rate. The MOH for the Borough of Lambeth highlighted the fact that treatment done in a hospital setting yielded a lower mortality rate. Of the 320 cases notified in 1908, 283 were removed to a hospital. 38 died in the hospital giving a case-mortality of 13.4%. On the other hand, 37 were treated at home. 6 died in the home setting giving a case-mortality of 16.2% (Lambeth 1908, 64). This is best explained by the fact antitoxin was more generally used in hospital treatment.

These are strong arguments in favor of the antitoxin treatment in hospitals. The saving of life would, moreover, have been still greater if only all the cases were treated by antitoxin at the earliest possible moment of the attack (Islington 1910, 4).

This has been clearly proved by the statistics of all hospitals, home, and foreign alike (Islington 1910, 4).

An unusual case

Although diphtheria is a disease that is spread by direct contact or air, the MOH of Waltham noted a case of diphtheria that occurred in the most unusual way.  A young lady, after dressing an abscess on a riding horse, developed a sore throat clinically suggestive of diphtheria and later confirmed by isolation of the diphtheria bacillus from throat swabs (Waltham Forest 1966, 7). There was little doubt that the horse (used in the preparation of diphtheria antitoxin) was the cause of the infection. Despite some perseverance necessary to secure its co-operation, there was no recovery of the germ from the horse’s throat and the source of infection remains a mystery (Waltham Forest 1966, 7).

Horses, diphtheria antitoxin and animal rights

Along with the discovery of the horse serum for eliminating diphtheria in 1894 was the founding of Victoria Street Society for the Protection of Animals Liable to Vivisection. This organization was an “anti-vivisection” group that advocated against the “support for the use of live animals in scientific research” (Hamilton, 66). Obviously, the obtaining of anti-toxin horse serum went against the ideologies of this organization. Although the organization had great popularity at first, and it gained some public supporters, the discovery of the diphtheria anti-toxin became a “low blow” due to its health benefits. It changed the organization’s goals into a “fringe movement” (Ritvo, 162). Even though the movement did get some rights passed, the diphtheria anti-toxin process remained viable under the argument that it helped so many people, and that if they wanted to get rid of it then they would have to get rid of “killing animals for food or for field sports” as well (Hackney 1936, 211). In addition to using horses to make antitoxins to neutralize the diphtheria toxin, there are numerous other applications where horses can be useful. For example, horses were once used as ambulances to transport the sick or wounded. Private businesses also found it economical to own a stud of horses to collect goods and make deliveries (Velten 2013, 56). Among the items that horses may transport, antitoxin against early stage diphtheria may be among the batch.


Diphtheria was once a highly contagious disease that took the lives of many. The disease was practically unsolvable, and only cured through means of delaying the disease for the patient by home remedies and clinical surgeries until the horse antitoxin serum was released in 1894. With the discovery of creating antitoxin using horse serum, the disease has become manageable. Though the disease today seemed to have eradicated from existence in the United States, it still remains a serious disease if immediate medical attention is not provided. Since the antitoxin does not neutralize the toxin that has already bounded to tissue, early administration is a key factor in making a full recovery. Delaying administration will not only allow the infection to spread, but is also associated with a higher mortality risk. The horse serum not only saved lives and made the pain a little more tolerable, but it also had the effect of helping to promote vivisection for the overall betterment of public health.

Primary Sources:

  1. Kensington 1896
  2. Kingston upon Thames 1897
  3. Stoke Newington 1897
  4. Hackney 1897
  5. Finsbury 1902
  6. Finsbury 1910
  7. Lambeth 1908
  8. London County Council 1910
  9. Islington 1910
  10. Hampton 1911
  11. Holborn 1925
  12. East Ham 1928
  13. Fulham 1933
  14. London County Council 1934
  15. Hackney 1936
  16. Hendon 1938
  17. Waltham Forest 1966

Secondary Sources:

  1. CDC Diphtheria
  2. Epidemiology and Prevention of vaccine-Preventable Diseases
  3. Hamilton, Susan. “Reading and the Popular Critique of Science in the Victorian Anti-Vivisection Press: Frances Power Cobbe’s Writing for the Victoria Street Society.” Victorian Review 36, no. 2 (2010): 66-79.
  4. Ritvo, Harriet . “Dangerous Classes.” In The Animal Estate: The English and Other Creatures in Victorian England (1987): 162
  5. Velten, Hannah. Beastly London: A History of Animals in the City. Reaktion Books, 2013.
  6. How horses helped cure diphtheria by Mallory Warner


L0017191 First English pony innoculated for diphtheria antitoxin 1894
“Tom, also known as Tommy first English pony innoculated for diphtheria antitoxine. Charles Sherrington wears a bowler hat, and Dr Marc Armand Ruffer stands by the pony’s head.” 1894 Credit: Wellcome Library, London